Method and device for refrigerating and/or freezing articles

ABSTRACT

A method and a device for refrigerating and/or freezing articles, in particular foodstuffs. The articles are conveyed by a conveyor belt through a treatment zone, where they are sprayed with a refrigerant from above through spray equipment. To prevent refrigerant from flowing down, a reflector level for collecting refrigerant is mounted beneath the conveyor belt. The conveyor belt and the articles on it are therefore additionally cooled from beneath.

This application claims the priority of German Application No.102004020180.3, filed Apr. 22, 2004, the disclosure of which isexpressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a method for refrigerating and/or freezingarticles, the articles being conveyed by means of a conveyor beltthrough a treatment zone in which a refrigerant is sprayed on them fromabove.

Furthermore, this invention relates to a device for refrigerating and/orfreezing articles, having a conveyor belt arranged in a treatment zonefor conveying the articles through said treatment zone and having sprayequipment mounted above the conveyor belt for spraying refrigerant ontothe articles.

For refrigerating and/or freezing articles, e.g., for maintaining thestability of foodstuffs or for hardening steel or for other structuralchanges, equipment is generally used for this purpose in which thearticles are conveyed by a conveyor belt through a treatment zone inwhich they are sprayed with a refrigerant. The refrigerant is usually aliquid gas, in particular liquid nitrogen or liquid carbon dioxide orliquid oxygen. For example, continuous freezing of foodstuffs is oftenperformed in tunnel freezers in which the foodstuffs are conveyedthrough the freezer on a conveyor belt and are refrigerated and/orfrozen in the process. If liquid nitrogen is used as the refrigerant, itis sprayed through spray nozzles from above onto the foods to be frozenin the rear area of the tunnel freezer, for example. Liquid nitrogenevaporates mainly directly on the foodstuffs. However, some of thesprayed liquid nitrogen does not strike the foodstuffs directly or itdrips off of the foodstuffs. This lost nitrogen then passes through theconveyor belt, usually made of a mesh belt, into the bottom part of thetunnel freezer, where it makes little contribution to the refrigerationcapacity.

The object of the present invention is therefore to provide a method ofrefrigerating and/or freezing articles, and a device for implementingthe method, so that the refrigerant is better utilized.

This object is achieved according to this invention in terms of theprocess by the fact that the refrigerant dripping off of the articlesand/or the refrigerant sprayed onto the conveyor belt is collectedbeneath the conveyor belt so that the refrigerant cools the bottom sideof the conveyor belt and the articles.

In terms of the device, the object of this invention is achieved by thefact that a reflector level for collecting refrigerant is mountedbeneath the conveyor belt.

This invention is based on the finding that the efficacy ofrefrigeration or freezing equipment may be increased if the liquid gaslosses are reduced. To do so, a reflector is installed beneath theconveyor belt conveying the articles, preferably in the area of theliquid gas injection. This reflector level keeps the refrigerant thatgoes below the conveyor belt in contact with the conveyor belt frombeneath and in this way cools the articles lying on the conveyor beltfrom beneath. When using liquid gas as the refrigerant, the liquid gasevaporates, cooling the conveyor belt and the articles. Therefore, asmuch heat as possible is removed from the articles to be refrigeratedand/or frozen. Furthermore, the articles are cooled as uniformly aspossible from all sides. Refrigerant dripping down without being used isthus used to improve the refrigeration process according to theinvention.

This invention is particularly interesting for refrigeration and/orfreezing equipment having a conveyor belt, e.g., a mesh belt, that ispermeable for the refrigerant. The refrigerant which is sprayed fromabove and does not come in contact with the articles to be refrigeratedand/or frozen but instead would pass through the conveyor belt is nowcaptured by the reflector level and collected. The refrigerant collectedhere makes a specific contribution toward cooling the articles frombeneath the articles. With traditional refrigeration or freezingequipment, however, the refrigerant passes through the conveyor beltinto the bottom part of the equipment, where it evaporates more or lesswithout being used.

The reflector level is preferably designed as a plate. Depending on thedesign of the refrigeration or freezing equipment, other forms of thereflector level are also conceivable.

To ensure effective cooling of the conveyor belt from beneath, thereflector level is expediently arranged at a distance of 0 mm to 40 mmbeneath the conveyor belt. If the conveyor belt is deflected at bothends of the refrigeration or freezing equipment, resulting in an upperconveyor belt conveying articles to be refrigerated or frozen and alower return conveyor belt, then the reflector level is mounted directlybeneath the upper conveyor belt.

According to a particularly preferred embodiment, the spray equipmentfor supplying the refrigerant is connected to a liquid gas source whichis designed in particular as a liquid nitrogen tank, a liquid carbondioxide tank or a liquid oxygen tank. Especially in combination with useof liquid nitrogen, this invention manifests its advantages inparticular. More enthalpy of evaporation is utilized for cooling theproduct per kilogram of nitrogen sprayed into the system. The efficiencyof the refrigeration or freezing equipment is thus improvedsignificantly. Furthermore, the specific refrigerant consumption (kgN₂/kg product) is also reduced.

Another positive effect that should be pointed out is that the reflectorlevel closes part of the flow cross section of the refrigeration orfreezing equipment for cold gas circulation. This reduces the cold gascirculation in the area of the nitrogen spraying. Less nitrogenevaporates on the path between the spray nozzles and the articles to befrozen, which increases the amount of liquid available and thusadditionally increases the cooling capacity on the articles. Inaddition, the product is cooled intensely not only from above (throughdirect spraying of liquid nitrogen) but now is also cooled from beneaththrough the evaporation on the reflector level beneath the articles tobe frozen. The refrigeration and/or freezing take(s) place much moreuniformly, more rapidly and results in a better product appearance afterrefrigeration/freezing.

This invention may be used with all conceivable refrigeration orfreezing equipment in which the articles to be refrigerated or frozenare conveyed on a conveyor belt through a treatment zone and arefrigerant is sprayed from above onto the articles. This invention maybe used to particular advantage for refrigerating or freezing foodstuffsin refrigerating tunnels.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a tunnel refrigerator inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION

The figure illustrates a tunnel refrigerator for freezing foods. Thetunnel freezer has a housing 1 in which is arranged a conveyor belt 2for conveying the foodstuffs. The foodstuffs 3 lie on the conveyor belt2 as they are conveyed through the cooling tunnel. On the path throughthe refrigerating tunnel, they are sprayed with liquid nitrogen fromabove through liquid nitrogen spray nozzles 4. The nitrogen gasatmosphere formed due to the evaporation of liquid nitrogen within thehousing 1 is circulated by a fan 5. The conveyor belt 2 is deflecteddownward at the rear end of the cooling tunnel over a deflector roller 6and returns as the bottom return conveyor belt 7. The conveyor belt 2consists of a mesh belt that is permeable for the liquid nitrogen.Therefore, liquid nitrogen dripping off of the foodstuffs 3 and liquidnitrogen sprayed directly onto the conveyor belt 2 next to thefoodstuffs will pass through the conveyor belt to the underside of theconveyor belt 2. In order for the liquid nitrogen not to run off intothe bottom part 8 of the refrigeration tunnel and evaporate therewithout being utilized, a reflector level 9 is mounted directly beneaththe upper belt 2. The liquid nitrogen passing through the conveyor belt2 is captured by the reflector level 9, which may be designed as asimple reflector plate, for example, and is collected so that theunderside of the conveyor belt 2 remains in contact with liquidnitrogen. This ensures that the conveyor belt 2 and thus the foodstuffs3 are additionally cooled from beneath.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. Device for refrigerating and/or freezing articles having a conveyorbelt situated in a treatment zone for conveying the articles through thetreatment zone and having spray equipment mounted above the conveyorbelt for spraying refrigerant onto the articles, wherein a reflectorlevel for collecting refrigerant is mounted beneath the conveyor belt.2. Device as claimed in claim 1, wherein the reflector level is a plate.3. Device as claimed in claim 1, wherein the reflector level is arrangedat a distance of 0 mm to 40 mm beneath the conveyor belt.
 4. Device asclaimed in claim 1, wherein the conveyor belt is as a mesh belt. 5.Device as claimed in claim 1, wherein the spray equipment is connectedto a liquid gas source.
 6. Method for refrigerating and/or freezingarticles, whereby the articles are conveyed by a conveyor belt through atreatment zone in which they are sprayed with a refrigerant from above,wherein refrigerant dripping down from the articles and/or refrigerantsprayed onto the conveyor belt is collected beneath the conveyor belt insuch a way that the refrigerant cools the underside of the conveyor beltand the articles.
 7. A device for refrigerating and/or freezingarticles, comprising: a conveyor belt situated in a treatment zone forconveying the articles through the treatment zone; refrigerant sprayequipment located in the treatment zone above the conveyor belt forspraying refrigerant onto the articles; and a reflector level locatedbeneath the conveyor belt such that sprayed refrigerant passing beneaththe conveyer belt is collected to cool the undersides of the conveyerbelt and the articles.
 8. A method for refrigerating and/or freezingarticles, comprising the steps of: conveying the articles by a conveyorbelt into a treatment zone; spraying the articles in the treatment zonewith a refrigerant from refrigerant spraying equipment located above thearticles; and collecting refrigerant passing beneath the conveyor beltbeneath the conveyor belt such that the collected refrigerant cools theunderside of the conveyor belt and the articles.